Pebble heater and method of converting hydrocarbons



Oct. 2l, 1952 R. K. SIMMs 2,614,968

\ PEBBLE HEATER AND METHOD 0E coNvERTrNG HYDEocARBoNs Filed Dc. 12, 1949 INVENTOR R. K. SIMMS Arron/VHS Patented Oct. 21, 1952 PEBBLE HEATER AND METHOD OF vCONVERTING HYDROCARBONS Russell K. Simms, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Application December 12, 1949, Serial No. 132,469

Claims. (Cl. 196-55) This invention relates to pebble heat exchangers. In one of its more specific aspects it relates to means for using pebbles of differentsizes and compositions in pebble heater apparatus. In another of its more specific aspects it relates to a method for carrying out multi-stage reactions or a plurality of reactions in pebble heater apparatus. In another of its more specic aspects it relates to improved pebble heat exchange appparatus.

p Thermal conversion processes which are carried out in so-called pebble heater apparatus utilize a fluent mass of solid heat exchange material which mass is heated to a high temperature by passing hot gas therethrough in a first direct heat exchange step and is then caused to contact huid reactant materials, furnishing heat thereto in a second direct heat exchange. The conventional pebble heater apparatus generally comprises two upright chambers which may be disposed in substantially vertical alignment. The solid heat exchange material is introduced into the upper portion of the rst chamber. That material forms a moving bed of solid heat exchange material which flows downwardly through the chamber in direct heat exchange with hot gaseous heat `exchange material. The solid heat exchange material is heated to a high temperature in the heat exchange and is then passed to a second chamber in which `the hoty solid heat exchange material is caused to contact the iiuid reactant materials in a second direct heat exchange relation, furnishing heat for the treatment or conversion of the fluid materials. y

Conventional pebble heater chambers of peb- `through the cylindrical bed, sometimes being introduced thereinto at the periphery of the bed and at its lower end, and are sometimes introduced through `a refractory arch which supports the moving pebble bed. At other times, heat is Vsupplied to the heatingchamber by supplyinga yfuel to the lower portion of the pebble bed within the heater chamber and burning the fuel on the surface of the pebbles so as to heat the pebbles by combustion and further heating the pebbles by passing the resulting combustion gas upwardly through the downfiowing fluent mass of pebbles. i

The heated pebbles are introduced into the up- 'per portion of a reaction chamber and reactant materials are introduced into the lower portion ofthe reaction chamber and. are caused to flow upwardly through the downowing fluent hot pebble mass therein, thereby obtaining the heat required for thermal conversion of the reactant materials. Reaction products are removed from the upper portion of the reaction chamber generally at points above the top surface of the pebblebed. One disadvantage which :is encountered in the use of conventional pebble heater apparatus is the fact that single reaction chambers are generally confined to single reactions therein. The high cost of pebble heater reaction chambers makes it economically desirable to utilize a single chamber for a plurality of concomitant reactions.

Broadly speaking, this invention comprises an improved means and method for carrying out multiple steps of reactions in a single reaction chamber. At least two groups of pebbles of different diameters are introduced into a pebble heater chamber. The pebbles may be catalytic or inert as desired. The groups of p'ebb-les are heated to different temperatures according to their sizes and compositions in an obliquelydisposed pebble heater chamber and are introduced into a reaction chamber at points disposed successively along the length of the reaction chamber. Reactant materials are introduced into-the lower portion ofthe reaction chamber where, if they are non-gaseous, they are partially or completely vaporized. The vapors are passed upwardly through the downflovving pebble mass and contact the pebbles of different sizes,. temperatures, and activity, and undergo the various stages of the desired reactions. The pebbles are recycled to the pebble heater chamber where they are heated and separated `according to size.

`Solid heat exchange material which is conventionally used in pebble heater apparatus is generally called pebbles The term pebbles as used herein denotes any solid refractory material of flowable size and form,` having strength, which is suitable to carry large amounts of heat from the pebble heating chamber to the reaction cham- 'ber` without rapid deterioration or substantial breaking. Pebbles which are satisfactorily used in pebble heater apparatus are substantially spherical in shape and range from about one- `eighth inch to about one inch in diameter. In

highest temperatures attained in the pebble heating chamber. of withstanding temperature changes within the apparatus. Refractory materials, such as metal alloys, ceramics, or other satisfactory material may be utilized to form such pebbles. Silicon carbide, alumina, periclase, thoria, beryllia, stellite, zirconia, and mullite may 'be satisfactorily used to form such heat transfer pebbles or may be used in admixture with each other or with other materials. Pebbles formed of such ma terials, when properly fired, serve very well in high temperatures. ,Some pebblessuchasimullite-alumina pebbles withstand temperatures above 3000 F. In the opera-tion off-the apparatus of this invention it is often. desirable'l to carry on one reaction in the presence of catalytic pebbles and another reaction in the,presence of in- The pebbles must also be capableI 4 I2 at a point adjacent pebble distribution membei' vI9' and is connected with the interior of shell I2. Valve member 25 is provided in fluid inlet conduit 24 so as to control the ow of fluid therethrough;

Pebble outletl conduit I1 is connected at its lower end to the` lower end portion of elevator ert pebbles in the same reaction chamber. In

one reaction, for example, dehydrogenation cataf lysts such as group V or group VI metal oxides, such as oxides of vanadium, chromiumor molybdenum, or an alumina base are used. It is desirable in the-formation of such pebbleslto utilize up to five per-cent byy weight oi. beryllium or magnesium oxide for stabilization purposes.v

An object of this invention is to provide an improved pebble heater apparatus. Another object of` the invention is to providev improved means for carrying out, multiplereactions in a single reaction chamber.. Another object of the invention is to provide means for carrying` on catalytic reactions in pebble heater apparatus. Another object of the inventionis to provide means for removing c'okefformed during the reaction of hydrocarbons. invention is toprovide means for utilizing coke formed in the reaction of hydrocarbons vto furnish heat for such reactions." Another object Aof the invention is to provide means for utilizing coke as one of the reactants in the reaction chamber. Other and further objects and ad'- vantages will be apparent to those skilled in the art upon study of the accompanying discussion and the drawings.

Understanding of the invention willjbe facilitated upon reference to the drawings in which Figure 1 is a schematic elevation of al pebble heater apparatus of this invention. `Figure 2 is a modified schematic elevation of a pebble heater apparatus of this invention. FigureB is a topview., partly in section, of the pebble heater chamber takenv on the 3--3 line of Figure 2.

Referring particularly to the device set forth as Figure 1 of the drawings, reactions chamber I I comprises shell I 2 which is closed at its upper Another 4object of the" and lower ends by closure members I3 and I4,

respectively. Pebble-inlet conduit I5 and eilluent outlet conduit I6 are `disposed in. closure member I3 and pebble outlet conduit I-1 extendsfrom the lower portion. of closure member I4. Additional eiuentoutlets are provided at intervals along the length of shell I 2v when a plurality of separate reaction products is obtained. These additional outlets are preferably in the form of support members 2| which extend to points adjacent the lower side of distribution members I8 and I9. Perforate pebble distribution members -I and -I 9.are disposed Vintermediate the ends of shell I2. Distribution members I8 and I9 are preferably formed as cones which are supported by support members 2l extending between shell I2 and pebble distribution members I 8v and I9. Pebble distribution members I8 andv I9 are smaller in outer diameter than the inner diameter/of shell I2. 3. Anf-an-A also 26. Pebble heating chamber 21 comprises obliquelyi rpositioned shell 28 which is closed at its upper and lower ends by closure members 29. and 3|., respectively, and a rotatable shell retained therein but not shown. Heating material inlet conduit 32 is provided in the lower closure member 3I and effluent outlet conduit 33 is provided in the upper end portion of shell 2B. Pebble conduit 34. extends between the upper end portion of elevator 26 and closure member 29 of pebble heater chamber 21. Pebble outlets 35, 3S, and 3'!` are disposed along the bottom side of chamber 21 intermediate the ends of lthat chamber. Outlets35, 36, and 31 may be in the form of hoppers which are provided with separation means, not shown, in th'eir upper ends along the lineV of the bottom of shell 28. Valves 38, 39,l and 4I are provided inthe lower ends of outlets 35, 36, and 31, respectively. Pebble conduits l24 and 43 extend from valves 39 and 4I, respectively,l to points immediately above and adjacent the apex of pebble distribution` members I8 and I9, respectively. Pebble inlet conduit I5v is connected to valve 3.3.

The` device of Figure 2 of the drawings is similarv to that shown and described as Figure l of the drawings. Like parts are identified by like numerals. Pebbleconduit 44 extends between valve 4I in pebblel outlet 31 and closure member I3 of shell I2. Pebble conduits 45. and 46 extend from valves 39- and 38, respectively, to points immediately above and adjacent the apex of pebble distribution members I8 and I9, respectively. Figure 2 is further modified by the addition of-a third fluid inlet conduit 41 which extends around at least a portion of shell I2 adjacent .pebble distribution member I8. Valve 43 is provided in conduit 41 to control the flow of uid therethrough.

Figure 3, which shows a partial section of pebble heater chamber 21, is provided with separation meanswhich comprises bars 49 and 5I .in the rotatable shell and over the upper ends of outlets 35 and 36. Bars 49 are spaced apart suiiciently to allow a rst portion of pebbles of a given size to fall therebetween but so as to prevent the passage of pebbles of a larger diameter therebetween. Bars 5I are spaced apart so as to allow a second portion of pebbles of a diameter larger than the first portion to fall therebetween but so as to prevent pebbles of a larger diameter from escaping therebetween. Outlet 31, which is provided in the lower end portion of chamber 21, receives pebbles of the largest size utilized in the pebble heater apparatus and therefore does not require a pebble separation means in its upper end. Although the separation means is specically shown as a plurality of spaced banmembers,

duced into the lower portion of chamber 21, the

fuel is burned in the presence of the pebbles in that chamber and resulting combustion gas is passed upwardly along the length of chamber 21 to eflluent outlet conduit 33 through which the eilluent material is removed. If a hot gas is utilized as the heating medium, that gas is introduced through inlet conduit 32 and after passing countercurrent to the ow of pebbles within chamber 21 is removed from that chamber through effluent outlet conduit 33. The pebbles having the smallest diameter are separated from the perforate distribution member I9 countercurrent to the flow of pebbles between pebble distribution members I8 and I9, tars and similar heavy high carbon content semi-solid materials are removed therefrom by the pebbles.. The v aporized materials are cracked either thermally or catalytically, depending upon the pebbles used,

at a temperature, for example, within the range of between 900 F. and 1200 F. In this process, mixed phase cracking is in many cases conducted and at relatively low pressure. That type of operation results in gasoline fractions having improved octane numbersover those produced by conventional processes for mixed phase crack ing in which it has usually beennecessary to Voperate at relatively high pressures to avoidat least localized phase. separations in cracking vcoils and resulting excessive lay-down of carbon. As the cracked materialspass through and around pebble distribution member I8 and upwardly countercurrent to the flow of pebbles above that support member, a normally gaseous hydrocarbon, such as propane or butane, isv introduced into chamber II through conduit 41 and polythe other pebbles within chamber 21 by allowing them to fall through the grill or grate formed by bars 49 in the rotatable shell and over the uppei end of outlet 35. Those pebbles of the smallest diameter therefore contact the heating gas for the shortest period of time and are therefore Araised to a temperature lower than the temperature of the other pebbles within the chamber. The pebbles of the next smallest size are removed through the grill or grate formed by bars`5l in the rotatable shell and over the upper end of outlet 36 and are contacted by the hot heating gas for a shorter period of time than are the largest pebbles which flow all the way through chamber 21 and are removed through pebble outlet 31. Separation of the pebbles is facilitated by rotating the inner rotatable shell. In this method of operation, therefore, the hottest pebbles are introduced into the upper end of chamber I I through conduit 44 and flow downwardly through that chamber as a contiguous bed. The pebbles which are of second highest temperature and which are removed from chamber'21 through pebble outlet 36 are introduced into chamber II through pebble conduit 45 and are Vdischarged therefrom immediately over the apex of pebble distribution member I8. The pebbles which are introduced into chamber II through conduit 44 and those which are introduced into that chamber through conduit 45 are mixed as they flow downwardly over the surface of pebble distribution member I8. The coolest pebbles are introduced into chamber II andare discharged from conduit 49 at a point immediately over the apex of pebble' distribution member I9. The mixture of the `hottest and the intermediate temperature pebbles is mixed with the coolest pebbles as they flow downwardly over the surface of pebble distribu tion member I9. t

In one method of operation a gas oil andtopped orreduced crude is preheated and partially or completelyvaporized or vis-broken. "The feed material is introduced into the lower portion of chamber II through valve 23 and inlet conduit 22. The feed materials are vaporizeda't a temperature within the range of between 600 F. and 900 F. during their contact with the cooler pebbles below pebble distribution member I9. As the vaporized materials iiow upwardlyl through f forming is carried out at a" temperature, for example, within the range of. between 1200 F. and 2000 F. The reaction products are removed from the upper portion of chamber I I through effluent outlet conduit IB. If desired, all of thefeed material may be introduced through inlet conduit 241and the. now of pebbles may be diverted from conduits 49 by closing valve 38 as desired.

A similar process may be utilized in the production of benzene. A hydrocarbon material within the range of from a normally gaseous material, such as butane, to a gas oil is charged vto the lower portion of the chamberthrough inlet coriduit 22. The feed material is vaporized at a temperature within the range of from 600 F. to to 900J F. during contact with pebbles below distribution member I9. The vaporized material is crackedto ethylene in the chamber portion between members IS and I8 at a temperature, for

example, within the range of between 900 F. and

l200 F. As the cracked materials pass .into the zone above baille I3, an aromatization or hydro- `cyclization reaction takes place and the ethylene is converted to benzene at a temperature, for example, within the range of between 1200a F. and 2000 F. i

In yet another method of the operation of the device shown as Figure 2 of the drawings, the smallest pebbles utilized in the system may con-` stitute a dehydrogenaton catalyst which. as has been disclosed, may be one of the group V or VI metal oxides. The balance of the pebbles may be inert and of one size. In such an operation, valve 39 maybe closed so as to allow the Vflow of pebbles only through pebble conduits 44 and 45 `or`valve 33 may be closed and valve 39 opened so as to utilize conduit 45 instead of conduit 45.. Ethane, propane, or butane is introduced into the lower portion of chamber II throughinlet conduit 22 and is dehydrogenated in the presenceof the dehydrogenation catalyst introduced into the lower portion of chamber II at a temperature Within the range of between 1000 F. and 1100D F. The balance of the pebbles are introduced into the upper portion of the chamber at a temperature ranging between 1700 F. and 1800 F. The hy- `drocarbon material which flows upwardly countercurrent to the flow of the pebbles in chamber I=I is converted to ethylene in the presence of the dehydrogenation catalyst. The ethylene reaction product ows upwardly through and around iiow of the catalytic pebbles. 4tion is catalytically cracked in the presence of 7 the pebble support members-and is contacted with the downiiowing pebbles at atemperature vwthir'i the range of between 1700" F. tov 1800" F.

lseparated from the other pebbles and are passed to an intermediate portion of chamber I I through conduits 45 or 45 at a temperature within the range of between 950 F. and l000 F. Inert pebbles within the range of between 1500 F. land 1650 F. are supplied to the upper end portion of chamber I I through pebble conduit 44. A cracked gas oil fraction is introduced into the lower portion of chamber II through inlet conduit24 and flows upwardly countercurrent to the The gas oil fracthe catalyst at a temperature of between 950 F. and 1l00 F. The cracked products liow upwardly through the chamber countercurrent to the flow of pebbles and is converted to condensed ring aromatics in the presence of the .pebbles ata temperature of between 1500" F. and 1650i F. Considerable carbon or coke is formed on Athe surface of the pebbles during the two conversions and under some conditions it is desirable to convert aportion of the coke to water gas. The conversion of coke to water gas takes place at about 1200 F. and higher. Steam is introduced into the lower portion of chamber II through inlet conduit 22 and flows upwardly through the bed of pebbles and coke material. The steam is superheated in the lower portion of the Vchamber and as it rises into that portion of the chamber at which a suficient temperature is obtained, .the coke material is converted to water gas, thereby regenerating the catalyst material. The water gas is removed from chamber II through conduit I6 together with the other reaction products and the mixture is passed to separation means, not shown, for separation of the resulting products. Any unconverted coke together with the pebbles is elevated to chamber 21 where a controlled surplus of oxygen is introduced through conduit 32 together with the heating material and the oxygen oxidizes the coke, thereby providing heat for the heating of the pebbles.

The device shown in Figure l of the drawings is especially desirable in those cases in which a vrapid. quench is needed to lower the temperature of reaction products. The hottest pebbles are inserted into chamber Il at a point in thelower portion of that chamber.y Reactant materials are introduced into the bottom of that chamber through inlet conduit 22 and flow upwardly `through the pebble mass, reacting in the presence 'of the hot pebbles.

vreaction chamber.

The device of Figure Al is also quite adaptable for use when one of the reactions is polymerization. Light hydrocarbons, such as C3, Ct, and C .hydrocarbons are introduced into the lower .portion of. the reaction chamber and are cracked at a temperature of between l000 F. and 1300" F.

Olens resulting from the reaction in the lower f portion of the chamber are contacted with'cooler pebbles in the upper portion of the reaction vchamber at a temperature-of, e. g., 600;F. to

1000u F. and are polymerized thereby.

The apparatus of this invention may be used in processes such as thermal and catalytic cracking as heretofore described; Visomerizatiom'for example, the conversion of butene-l to is'obutylene; dehydrogenation, for example, the conversion of ethylbenzene to styrene; condensation,l for example, the reaction of ethylene with butadiene to form benzene; vand high temperature alkylation employing hydrogen or carbon dioxide asa catalyst. l

Pebble heater chamber 21 is obliquely'disposed at an angle from the horizontal as heretofore disclosed. The chamber is preferably disposed-,at an angle of between 5 and-30 from the horizontal. Such positioning assures good pebble flow through the pebble heating chambervduring the heating operation.

Disclosure herein has been substantially limited to countercurrent flow of pebbles and reactants. The device of this invention may be .used to provide concurrent flow through one chamber portion and countercurrent -flow through another portion. For example, when'a fuel oil or residuum is introduced into the vchamber near its upper end, concurrent flow of that material and the heated pebbles is obtained. Steam, hydrogen, or a light hydrocarbon may be introduced into the lower portion of the. chamber and ow countercurrent to the flow 'of pebbles through a portion of the chamber, thereby superheating, preheating, or cracking those fluids which are subsequently admixed with the downflowing oil to effect cracking, hydrogenolysis, polyforming, hydroforming, gas reversion, Ior cracking. l Y

The process of this invention may be modified by screening the pebbles to separatethem into streams of various size pebbles. The streams are then passed to separate heating. chambers where they are heated to temperatures at which they are to be utilized in the reaction chamber. Conduite 44, 45, and 46 are attached to the separate heating chambers in such a modifie process. i

The combination of processes with which the pebble heater apparatus of this invention may be used advantageously are many and are. varied. It is believed that many modifications and advantages will .be apparent to those skilled in the art upon study of the accompanying disclosure and the drawings. Such modications' are deemed to be within the spirit and the scope of this disclosure.

I. claim:

l. An improved pebble heater apparatus comprising in combination a .rst closed upright shell; a first pebble inlet in the upper endportion of said first shell; at least one additional'pebble .inlet in said rst shell intermediate its ends; a first Vfluid inlet in the bottom portion of said rst shell; a second fluid inlet in said first shell-adjacent the level of at least one said additional pebble inlet therein; a second'closed shell obliquely positioned above said first shell; a first pebble conduit extending between the bottom side of said second shell and said viirst pebble inlet in said rst shell; an additional pebble conduit extending between another point on the bottom side of said second shell andl each said additional pebble inlet in lsaid rst shell; pebble separation means in the upper ends of at least all yexcept-the lowermost said pebble conduits `extendingfrom.

the bottom side ofv saidv second shell, said pebble separation means providing progressively widery openings into progressively `lower pebble` con-` duits; an elevator; asecond pebble conduitextending between' the lower end of `said first shell tion of saidsecond shell. l

i 2. An improved pebble heater appara-tus comprising in combination a iirst closed upright shell; a rstpebble inletin the upper end portion of said first shell; `anellluentgoutlet conduit in the upper end portion of said rst shell; at least one additional pebble inlet-in said first shell intermediate its ends; a first shell inletfin the bottom portion of said. lirst shell; a second` `iluid inlet in said iirst shell adjacent the level of at least one said additional pebble inlet therein; a second closed shell obliquely positioned above said` iirst shell; a 'first pebble conduit` extending between the bottom end portion of said second shelland said first pebble inlet in said first shell; an additional pebble conduit extending between points disposed along the bottom side of said second shell and each said additional pebble inlet in said rst shell; pebble separation means in the upper ends of at least all except the lowermost said` pebble conduits extending from the bottom side of said second shell, said pebble separation means providing progressively wider openings into progressively lower pebble conduits; an elevator; a second pebble conduit extending between the lower end of said first shell and the lower end portion of said elevator; a third pebble conduit extending between the upper end portion of said elevator and the upper end portion of said second shell; heating'material inlet means in the lower end of said second shell; and eiiluent outlet means in the upper end portion of said second shell.

3. The pebble heater apparatus of claim 2, wherein at least one conical baille member is coaxially disposed in said rst shell, intermediate its ends and spaced from the walls of said rst shell so as to form an annulus for pebble iiow therebetween; one of said additional pebble inlets extending to a point overI the apex of each said conical baffle; said rst pebble conduit extends between the lower end portion of said second shell and said first pebble inlet in said rst shell; at least one pebble separation means in the bottom side of said second shell; and one of said additional pebble conduits extending between said separation means and each said second pebble inlet.

4. The pebble heater apparatus of claim 3, wherein said second shell is disposed at an angle between and 30 from the horizontal.

5. The pebble heater apparatus of claim e, wherein -a rotatable shell having at least two separation means therein is provided in the bottom side of said second shell, said separation means comprising a grill extending around said rotatable shell and the bars of the grill nearer the upper end of said second shell being spaced closer together than in each succeeding grill in said second shell.

6. The pebble heater apparatus of claim 1, wherein at least one conical baille member is coaxially disposed in said first shell, intermediate its ends and spaced. from the walls of said first shell so as to form an annulus for pebble ilow therebetween; one of said additional pebble inlets extending towa pointaover the apex of each said conical baille; said second shell is obliquely positionedabove -said rst shell at an angle of from 5 to 30 from the horizontal; a rotatable shell in said second shell; at least one pebble separation means `in said rotatable shell; said rst pebble'conduit extends between the pebble outletbelowithe separation means nearest the upper end of said second shell and said iirst pebble inlet; `and `one ofcsaid additional pebble `conduits extending betweenfeach successive pebble outlet pointin the bottom side of said second shell and one ofl said additional pebble inlets which extends to a point over one of `saidconical baflles disposed successively lower in saidiirst shell.

A methodffor subjecting hydrocarbons to different reaction temperatures in `a single reactionizonewhichcomprises introducing a iirst portion' lof relatively large diameter pebbles into the upper endportion of a reactionzone at a temperature within the range of `between 1200o F. and 2000 F.; introducing at least one other portion ofpebblesofa `diameter smaller than said lirst portion into said reaction zone at a point intermediate its upper end portion and its lower end portion and at a temperature within the range of between 600 F. and 1200 F.; introduc` ing a `hydrocarbon fluid into the lower portion of said reaction zone; reacting said hydrocarbon fluid in the presence of a mixture of said pebbles at a temperature within the range of between 600 F. and 1200 F.; passing resulting reaction products upwardly in said reaction zone into contact with said larger pebbles at a temperature within the range of between 1200 F. and 2000 F.; reacting said reaction products in the presence of said hotter pebbles; removing resulting reaction products from the upper portion of said reaction zone; gravitating said pebbles from the lower por- `tion or' said reaction zone, elevating said pebbles to a single pebble heating zone; heating said pebbles in said pebble heating Zone; separating said smaller pebbles from said larger pebbles in said pebble heating zone and gravitating them from said pebble heating Zone to said intermediate point oi said reaction chamber upon reaching a temperature within the range oi' between 600 F. and 1200 F.; further heating said larger pebbles in said pebble heating zone to a temperature within the range of between l200 F. and 2000" F.; and gravitating said larger pebbles from said pebble heating zone into the upper end portion of said reaction zone.

8. Avmethod for subjecting hydrocarbons to different reaction temperatures in a single reaction chamber which comprises heating pebbles of a plurality of sizes in a single pebble heating zone at different temperatures according to peb` ble sizes; gravitating a first portion of said pebbles of a smaller size from said heating zone at a first reaction temperature to a given level in a reaction zone; gravitating additional said pebbles of at least one successively larger size and at a dierent reaction temperature than said iirst pebbles from said heating zone to at least one other level within said reaction zone successively disposed from said rst pebbles according to successive temperatures of said successively larger pebbles; gravitating said pebbles through said reaction zone as a contiguous mass; introducing a hydrocarbon fluid into the lower por- 11 tion ofv said 'reaction zone; passing 'said hydrocarbon uid upwardly through .said reaction zone, whereby said hydrocarbon fluid is successively reacted in direct heat exchange with pebbles at successively higher temperatures; removing re-vr sulting reaction products from the upper portion of said reaction zone; gravitating said pebbles from the bottom of said reaction zone; and elevating said pebbles to said pebble heating zone.

9. A method for subjecting hydrocarbons to diierent reaction temperatures in a single reaction chamber which comprises heating pebbles of a plurality of sizes in a single pebble `heating zone at different temperatures according to, pelo-` ble sizes; gravitating smaller pebbles vfrom Said heating zone at a lower `reaction temperature. .t0 a given level in thelower portion of a .reaction zone; additionally heating successively larger pebbles in said heating zone; successively gravitating said successively larger pebbles at successively higher reaction temperatures .from said pebble heating zone to successively higher levels within said reaction zone; gravtatin-g said pebbles through said reaction zone as .a lcontiguous mass; introducing a hydrocarbon fluid into 4the lower portion of said reaction zone; passing said hydrocarbon fluid upwardly through said reeel tion zone, rst reacting; said hydrocarbons in cone tact with said lpebbles atA the lower temperature and :then successively reacting rresulting reaction products in direct heat exchange with :the suce cessively hotter pebbles; removing resulting re-l action product from the upper portion or seid reaction zone: eravitating said pebbles from the bottom of said reaction zone; and elevating- Seid pebbles to said pebble heating zone..

1.0., The method of. claim 8, vwherein Seid Smaller pebbles are gravtated into the upper end por-.- tion of said reaction zone and successively lolger pebbles are srevteted into said reaction zone et successively lower 1eve1- RUSSELL K- SIMMS.

REFERENCES CITED The following references .are of record in the 

7. A METHOD FOR SUBJECTING HYDROCARBONS TO DIFFERENT REACTION TEMPERATURE IN A SINGLE REACTION ZONE WHICH COMPRISES INTRODUCING A FIRST PORTION OF RELATIVELY LARGE DIAMETER PEBBLES INTO THE UPPER END PORTION OF A REACTION ZONE AT A TEMPERATURE WITHIN THE RANGE OF BETWEEN 1200* F. AND 2000* F.; INTRODUCING AT LEAST ONE OTHER PORTION OF PEBBLES OF A DIAMETER SMALLER THAN SAID FIRST PORTION INTO SAID REACTION ZONE AT A POINT INTERMEDIATE ITS UPPER END PORTION AND ITS LOWER END PORTION AND AT A TEMPERATURE WITHIN THE RANGE OF BETWEEN 600* F. AND 1200* F.; INTRODUCING A HYDROCARBON FLUID INTO THE LOWER PORTION OF SAID REACTION ZONE; REACTING SAID HYDROCARBON FLUID IN THE PRESENCE OF A MIXTURE OF SAID PEBBLES AT A TEMPERATURE WITHIN THE RANGE OF BETWEEN 600* F. AND 120O* F.; PASSING RESULTING REACTION PRODUCTS UPWARDLY IN SAID REACTION ZONE INTO CONTACT WITH SAID LARGER PEBBLES AT A TEMPERATURE WITHIN THE RANGE OF BETWEEN 1200* F. AND 2000* F.; REACTING SAID REACTION PRODUCTS IN THE PRESENCE OF SAID HOTTER PEBBLES; REMOVING RESULTING REACTION PRODUCTS FROM THE UPPER PORTION OF SAID REACTION ZONE; GRAVITATING SAID PEBBLES FROM THE LOWER PORTION OF SAID REACTION ZONE, ELEVATING SAID PEBBLES TO A SINGLE PEBBLE HEATING ZONE; HEATING SAID PEBBLES IN SAID PEBBLE HEATING ZONE; SEPARATING SAID SMALLER PEBBLE FROM SAID LARGER PEBBLES IN SAID PEBBLE HEATING ZONE AND GRAVITATING THEM FROM SAID PEBBLE HEATING ZONE TO SAID INTERMEDIATE POINT OF SAID REACTION CHAMBER UPON REACHING A TEMPERATURE WITHIN THE RANGE OF BETWEEN 600* F. AND 1200* F.; FURTHER HEATING SAID LARGER PEBBLES IN SAID PEBBLE HEATING ZONE TO A TEMPERATURE WITHIN THE RANGE OF BETWEEN 1200* F. AND 2000* F.; AND GRAVITATING SAID LARGER PEBBLES FROM SAID PEBBLE HEATING ZONE INTO THE UPPER END PORTION OF SAID REACTION ZONE. 